How to reduce amount of edge lines as in picture?
A better workflow would be to use “Loop Cuts” to form the edges of your doors and windows. In “Edit Mode” place you cursor near an appropriate edge and press “CTRL” + “R” then right Mouse click to insert it then you can move it by moving the mouse. When satisfied “Right mouse click to lock it into place. Rinse and repeat for the other edges.

If you need to delete an edge loop press “X” then select “Edge Loop” from the drop down menu.

If you need to move an edge loop after the fact press “CTRL + “E” and select “Edge Slide” from the drop down menu. This will work for a section of an edge loop as long as it is bound by at least two vertices.